Notice how Bains guide words it plainly. https://dl.dropboxusercontent.com/u/63112396/ec.png

Specifically calling them "ingredients".
The secret has to do with a set of masks, material and pattern. For right now I dont think that color matters since there is no clue to a color set.

Going by the link i found above, I feel even stronger about Firestarter than I do Rats or any other mission. The author speculates that the astrological symbols in the guide have something to do with an alchemy ingredient needed to get to the secret.

My hunch is that specific combinations of masks colors and patterns will trigger something. So when I went back to the guide to check, I found this section https://dl.dropboxusercontent.com/u/63112396/ec.png , the wording Bain chose could have been completely different yet he chose to call them "ingredients".

Is there even a way into the vault without turning off the power?

EDIT: I found this http://www.reddit.com/r/payday2secret/comments/1ntc8g/a_bit_of_light_on_bains_guide/

But to also add to all this information, Im very sure that the webseries and game secret have something in common. The first secret had multiple references to biblical quotes, while in the newest webisode these references make a comeback out of the blue. making me think that we should also be considering paying much more attention to the webseries.

Ex. On episode One, Wolf is shown putting on a wig very similar to this http://i.imgur.com/9PpShtO.jpg person getting helped up. ....just a thought.